In many synchronous dynamoelectric motor applications, amortisseur or rotor pole face bar windings are customarily employed for augmenting the motor starting torque. The amortisseur windings of the various rotor poles are shorted together so that the synchronous motor essentially acts like an induction motor whenever the rotor speed deviates from its synchronous speed, such as during the initial start-up and acceleration to synchronous speed. When the synchronous speed is reached, the relative slip between the rotor and stator fields becomes negligible, and little or no current is conducted by the amortisseur windings.
In conventional practice, the amortisseur bar windings for each pole are brazed or welded to a shorting ring associated with that pole. Shorting rings associated with adjacent rotor poles are then electrically and mechanically interconnected by a conductive strap brazed or bolted thereto.